Unité: Interactions moléculaires Flavivirus-Hôtes
Responsable: Desprès Philippe
The Flavivirus-Host Molecular Interactions laboratory has been established in January 2002. The research programs are conducted to improve the knowledge of the molecular mechanisms that contribute to the pathogenicity of mosquito-borne flaviviruses responsible for emerging human arboviroses such as dengue hemorrhagic fever and West Nile encephalitis. Understanding the molecular basis of the host-pathogen interactions in mosquito vectors and mammalian hosts and the consequences of these interactions on the severity of flavivirus infection will offer important insights into viral diagnostic and effective vaccine designs as well as therapeutic strategy.
Molecular basis of mosquito-dengue virus interactions
(V. Mayau ; program leader: A. Delécluse)
Mosquito populations display variable susceptibility to flavivirus development, termed " vector competence ". Competence reflects the different barriers encountered by the virus from its entry into the mosquito midgut to the release in the saliva. Various factors including specific mosquito receptors and differential viral replication in the mosquito are critical in the competence. Molecular approaches are developed to identify the cellular factors responsible for vector competence to dengue (DEN) virus.
The host genetic determinism of susceptibility to flavivirus infection
(A. Kajaste-Rudniski and M. Lucas ; program leader: P. Desprès )
We reported that the severity of WN virus experimental infection of mice correlated with the occurrence of a point mutation in the Oas1b gene that leads to a defective form whereas resistant mice to WN virus infection have an intact Oas1b protein. The interferon-inducible Oas1b gene suppresses WN virus infection through an Oas1b-mediated anti-viral pathway restricting viral replication inside cell. Because Oas genes are candidates for having a role to differential susceptibility to flavivirus infection, a particular emphasis is made on their genetic polymorphisms in humans. (Coll.: J-L. Guénet and C. Julier).
Innate immunity to DEN virus
(E. Navarro-Sanchez ; program leader: P. Desprès )
The project is based on the question how interstitial dendritic cells (DCs) respond to DEN virus infection at the anatomical sites where virus replicates after the bite of infected mosquito. We reported that DC-SIGN, a membrane protein with a lectin ectodomain, is essential as attachment receptor for the productive infection of human DCsDC-SIGN+ by mosquito-derived DEN viruses. The potential impact of molecular interactions between DCsDC-SIGN+ and DEN virus on their activation and induction of a specific innate immune response to DEN virus has been investigated (Coll.: F. Arenzana, A. Amara and F. Rey).
The apoptotic properties of viral sequence ApoptoM
(A. Catteau ; program leader: P. Desprès)
We showed that intracellular transport of the membrane M protein through the secretory pathway results in induction of apoptotic cell death. The death-promoting activity of flavivirus M protein reflects the proapoptotic properties of an internal nine-residue sequence referred to as ApoptoM. Whether cytotoxicity of M results from molecular interactions between ApoptoM and trans Golgi-specific apoptosis mediators is a critical issue that has been investigated (Coll.: A. Amara).
The biological properties of flavivirus NS1 glycoprotein
(program leader : M. Flamand)
We reported that glycoprotein NS1 is secreted as a unique hexameric species in the culture fluids of dengue virus-infected primate cells. In vivo, we found that NS1 circulates in the blood stream of most patients during the acute phase of dengue virus infection. In mice, hexameric NS1 appears to accumulate the liver. In vitro, extracellular NS1 can be endocytosed by different target cells such as hepatocytes and endothelial cells. In both cell types, the protein resides within lysobisphosphatidic acid-rich structures reminiscent of late endosomes. Questions regarding the mode of entry of the NS1 protein, the signaling pathways that may be triggered during endocytosis and their possible contribution to the physiopathology of disease are addressed. (Coll.: M. Arborio, J. Gruenberg, I. LeBlanc, S. Kayal).
Diagnosis of flavivirus infections based on the detection of seric non-structural NS1 antigen
(MT. Drouet and P. Matthieu ; program leader : M. Flamand)
We have generated a diagnostic tool designed for the detection of ongoing dengue virus infections that is now entering industrial development (in collaboration with Bio-Rad). The innovative approach consists in the capture of nonstructural glycoprotein NS1 in patients' sera during the clinical phase of infection. An antigen-capture ELISA offers many advantages compared to the other currently available methods. Indeed, specific antibodies can be detected by ELISA but not during the early phase of the disease and RT-PCR cannot be routinely used to establish an ongoing flaviviral infection. We are investigating whether NS1 antigen may constitute a reliable marker for other flaviviral infections.
Design of effective vaccines against flavivirus-induced diseases
(M. Lucas and MP. Frenkiel ; program leader: P. Desprès )
We have evaluated the efficiency of measles virus (MV) vaccine, a live negative-stranded RNA virus, and the defective lentivirus HIV-TRIP for prevention of West Nile encephalitis. The WN virus sequence encoding the envelope E-glycoprotein was inserted into genomes of MV and HIV-TRIP vectors. Immunization of mice with live MV or non-replicating HIV-TRIP expressing the WN E-glycoprotein protected against a lethal challenge with WN virus. Thus, lentiviral vector and pediatric MV vaccine expressing flavivirus antigens have the potential to elicit long-term humoral immunity against flavivirus infection (Coll.: P. Charneau and F. Tangy).
Mots-clés: Flaviviridae, flavivirus, virus à ARN, arbovirus, maladies émergentes, maladie tropicale, dengue, fièvre du Nil occidental, génétique de sensibilité, compétence vectorielle, pathogenèse virale, virulence virale, diagnostic viral, développement vaccinal, apoptose, immunité innée, virologie moléculaire